Process of recovering tin



March 1s, 1924; '11,487,125

K J. R. STACK PROCESS OF REG OVERING TIN Original Filed Jan. 4, 1'922 ANDBL' /NsoLUno/v IN V EN TOR A TTORNE Y Patented Mar. 18, 1924. I

UNITED' ,STATES PAT-ENT j OFFICE.

.application meannuary 4, 1922, serial m. 526,871'.

To all whom t may concern.'

Be it known that I, JAMES ROBERT STACK, a citizen of the United States, and resident of Perth Amboy, in the county of Middle- 5 vsex and State of New Jersey, have invented certain new and useful Improvements in Processes of Recovering Tin, of which the following is a specification.

This invention relates generally to a process for the treatment of complex bullion and alloys containing tin, bismuth and similar metals to recover the values contained therein.

My method, considered broadly, comprises a method of separating and recovering certain metals and particularly bismuth and tin from complex alloys containing lead,

copper, antimony, arsenic and the precious metals, by subjecting the impure bullion or alloy to electrolysis under conditions that will cause the bismuth solution and the other metals to be precipitated with the slimes, and then separating the bismuth and tin.

The process also comprises an improved method of separating the tin and bismuth remaining in solution after their separation from other metals, such as lead, copper, antimony and the like, by precipitating the bis- `muth either as a commercial product or as a compound susceptible of treatment by standard methods to produce a commercial product, and then recovering the tin in a commercial condition. The invention further consists in treating impure bullion and alloys containing bismuth and tin by a practically continuous process that first separates the bismuth and the tin'by precipitating all or substantially all of the lead, copper, antimony, arsenic and the precious metals by electrolysis and causes such metals to be deposited as slimes in the form of compounds or alloys easily refined to produce commercial products; then bychemical substitution precipitates the bismuth and any traces remaining of the other metals to produce a solution containing tin in the formof a salt, and finally recovers the tin in commercial form from the solution.

Although the process may be utilized in the treatment of lmpure alloys and bullions containing various complex mixtures of and tin to remain in Renewed January 14, 1924.

metals, it will be described with special reference to the treatment of slimes recovered in the electrolysis of impure tin bullion produced by reduction of Bolivian or Colombian ores, which contain a large number of other metals in greater or less. amounts, in addition to the tin and bismuth content. Relatively large quantities of anode slimes are produced in the primary treatment of such impure bullion, which contain appreciable quantities of tin occluded with the other metals. In practice approximately seven to ten percent of anode slimes are produced for each ton of vbullion treated, and these slimes occlude approximately two per cent of the total amount of tin contained in the.

ore. A considerable portion of the lead resent in the slimes, for exam le, as hig as 50%, may be present as lead) part of the tin is present as finely divided metallic tin. e remaining portion of the tin and of the lead, together with the other nlitals found in the ore, form a complex a oy.

complete reduction in a suitable reverberatory or blast furnace. About 1400 to 1500 pounds of metallic alloy will be made from one ton of slimes. This alloy is cast into anode plates v of suitable dimensions and weight that will have approximately the following composition:

Au .165 ozs. per ton.

Ag 78 99 s s Bi 35%. y

Reference is made to the drawin which shows a How sheet illustrative of t e steps of the process hereinafter described.

Referring to the drawing, the plates 2 as anode are then subjected to electrolysis in a vat 4 of any suitable or well known construction. The cathode 6 may/be a sheet of lead, copper, iron or of tin, and it is se arated from the anode by a semi-permea le partition or membrane 8 of any preferred construction,for example, ed in .an unglazed clay cell that Ywill prevent In practice the slimes are first smelted toi by being inserti` sulphate, and

leo

mechanical mixing or 'didusion of the electrolyte while permitting passage of the current by migration or ionic didusion. r)The anolyte 102 maybe hydrochloric acid solucathode, provided only the electrolyte is adapted to take both tin and bismuth into solution upon the passage.. ol the electrov lytic current.

A circulation or other suitable means.

l the constituents ol the anode,

the temperature,

During electrolysis the temperature oil the electrolyte is maintained approximately at 100 ll., while stratification is preventeAd l rect current of about 550 amperes is applied, corresponding to a current density of ap- 'proximately 20 amperesper square foot o' anode surface with a voltage of approximately 2%.l Both the amperage and the voltage may vary somewhat depending on v the composition of the electrolyte and and goed results have been density of from 20 to 30 amperes and obtained with a a voltage of from one and lone-hall to two and f/ to the bottom of jected to any one of When the solution one-halt volts.

rl`he' metals ofthe anode gradually dissolve, 'not however according to the potential series, but asa complex alloy of bismuth,-

arsenic and lead. rlhe lead will he precipitated in the oooh-moderately dilute hydrochloric acid solutiony as PbGl2, which is insoluble and falls to the bottom of the tank with the` slimes. IThe tin, antimony, copper,

t arsenic will also belprecipitated Ain the metal-` lic state by tin chloride,

the yreaction .being approximately as follows:

anser-tester:emmener.

All of the old and silver and substantially all of the le copper, arsenic and antimony are thus contained in the' slimes which settle the tank and may be removed and treated in any suitable way for the recovery of these metals, Preferably the slimes aref ilter pressed and vthen subthe numerous methods now in common use,.such, for example, as the methods employed in refining' or softening and liquating lead; which will result in the complete separation oil the lmetals with recovery ofthe total values contained.A l

The reactions are not to be understood as being absolutely quantitative, however, because negligible percentages` 'l and arsenic may remain in the solution and be lremoved later, as hereinafter described. has 'become saturated with metallic salts, sequent treatment to recover the dissolved metals. ln case the anodes have not been totally dissolved, apid solution may approximately 18% ',acid.J

'being subjected f or refactory alloys.

it is removed for sub-.-

be added and the treatment continued until the anodes are reduced to scrap.

'lhe saturated solution. alter removal trom the electrolyzing vat l is conducted to a precipitation tank 1l of any desired coustruction, is heated to a temperature ol about F, and preferably is vigorously agitated by air introduced under slight pressure. A quantity of metallic tin or other metal or metals above bismuth in the E. M. F. series is then added to the solution, which causes relatively rapid precipitation of the bismuth and any arsenic, and antimony in a finel divided ilorm known as bismuth cement. Ylhe solution in which( the metallic equivalent or tin, in place of the other metals, has been dissolved is then allowed tocool and settle and the supernatantl liquid decanted. rll`he bisil muth cement that settles to the bottom ot the tank can be refined by any well known rocess, and without further treatment, can

e disposed of as a standard product of commerce.

The liquid decanted will contain approximately from twelve to fifteen per cent oil tin in the form of tin( chloride, and will be entirely free from other metals except slight traces which may be removed by the addition of fresh acid and a longer period of treatment, or which may be disregarded, as they do not affect the commercial value of the final product. rlhe tin chloride can be reduced'to a commercial product by various methods or it may be evaporated and sold as bichloride of tin solution, or the tin chloride may be crystallized and the crystals marketed. ll it is desired to produce metallictin, this may be accomplished in various ways, for example, by evaporating the chloride solution to a smallbulk and mixing;

. the same with calcium oxide to a thick paste,

which is allowed to set, and is then smelted for the recovery of metallic tin.

Byl my improved process the tin is recovered in a state of unusual purity without to kmetallurgical processes to renne the metal and remove impurities therefrom. The metals arrangethemselves in cachot the stepsof the process in groups which are vreadily reduced@ and separated without the formation of further The lead, copper and arsenic are almost completely removed in the first step of the operation with the slimes 'precipitated at the bottom of the electroytic vat. The antiinony `and the other metals that may remain in small amount are separated and removed with the bismuth as a bismuth cement, which is also readily treated to separate the constituent metals according to well known .standard practice for the refining of such-material. @onsequently--the process possesses marked advantages not only beca or the high purity remaining copper,

etv

complex ien iat

of my of the final products obtained but also because the intermediate and secondary products of the several steps toward the desired result are of a character and of a composition which will permit them readily to be Aassimilated in the practice of established commercal metallurgical plants.

` Although I have shown and described and have pointed out in the annexed claims, certain novel features of my invention, it will be understood that various omissions, substitutions and changes in the several steps process andin its operation may e made by those skilled in the art without departing from the spirit of the invention.

What I claim is: a

1. The process of refining impure tm bullion to recover the contained metals, which consists in subjecting the bullion as anode to an electrolytic current of appropriate voltage and amperage in an electrolyte capable of holding tin and bismuth in solution andv depositing substantially all of the other contained metals as slimes or precipitates,

^ and then se arating the tin from the bismuth and ot er metals by precipitating the bismuth and retaining the tin in solution.

2. The process of refining impure tin bu-llion to recover the contained metals, which consists in passing a current of a propriate voltage and am erage from the ullion as anode to a cathode separated from the anode by a semi-permeable membrane through an electrolyte capable of combining with vtin and bismuth to form soluble salts and Awhich will deposit a substantial portion of each of the remaining metals as slimes, then pre,-

" cipi'tating the bismuthv and other metals by rate] 3. The process of refining impure tin bul-` addmg an excess of tin to the solution and treating said solution and the slimes sepay to recover the metal values thereof.

` lion to recover the contained metals, which solution, which will lform consists in assing an electrolytic current from the bu lion as anode to a cathodevseparated from the anode by a diaphragm -permitting ionic diffusion through an electrolyte capable of holding tinand bismuth in a non-soluble salt of lead and react with the compounds of arsenic to deposit metallic arsenic as slimes, then adding an excess of tin' to the electrolyte to preclpitate bismuth and other metals contained therein, and recovering the values contalned in lsaid slimes and solution.v

4. In vthe electrolytic refining of complex method of separating tin and bismuth which consists in passing a current of appropriate voltage and amperage from the alloy as anode to a cathode separated from the anode by. a semi-permeable lmembrane throu h an electrolyte' which will take the tin an bismuth into solution and preci itate .the lead as a non-soluble salt, and t en separating vto 110 F., precipltating the cover and the tin by adding a precipitating the solution to form a non-solub e cement.

agent to bismuth 5. In the electrolytic refining of complexy alloys the method of forming a bismuth cement from the electrolyte containing tin, bismuth and other metals in solution, which consists in passing an electrolytic current of .sists 1n passing an electrolytic current hav-- approximately one-half toI ing a yvoltage of two volts and a current density of from 20 to 30 amperes from .the alloy as anode to the cathode Aseparated by a semi-permeable diaphragm through4 an electrolyte ada ted to hold the tin in sol n the same to a temperature of' approximate y 110 F., adding an excess of metallic tin to the to precipitate the other metals contained therein, and then recoverin the tin.

v7. In the electrolytic re ning of impure bullion and complex alloys to recover tin, the method which consists in passing an electrolytic current of approximately 20 to 30 amperes and one to two volts from the alloy as anode to a cathode electrolyticallyv insulated from the anode through an electrolyte heated approximately tof"v F., which bismuth into solution on current, removing the sothe same approximately bismuth, antimony, arsenic and copper as a bismuth cement and then recovering-the tin.

8. In the electrolytic refining of complex alloys the ing the gold, silver, lead andarsenic and a portion of the copper and antimony from tin and ,bismuth by passinga current of appropriete amperage and-voltage from the alloy as anode to a cathode separated from takes the tin and the paing of the lution an `heating solution I ution, removing t e solul'tlon from the slimes, heatin method which conslsts in separatl the anodeby a semi-permeable membrane `through .an electrolyte containing hydrov chloric acid heated to a temperature of 100 F.,lunti1 the tin, bismuth and portions of the other metals are dissolved, removing the solution withthe dissolved metals, heating the same'to a temperature' of approximately 110 F., lprecipitating the bismuth, arsenic, antimony and copper as a bismuth cement and the-n recoveringA the tin.

9. In the electrolytic treatment of complex I alloys 'containing tin `and bismuth to resepara the metals therein, the

and bismuth into solution on the passage e the current and to precipitate lead and ar- 'ot the shmes orous diaphragm between' the cathode an the anode during electrolysis, then removing the solution and heating` the same to a' temperature ot approximately 110 iF. and agitating the same with air, adding a metal havinga higher potential than bismuth to precipitate any antimony, arsenic, copper and bismuth as a bismuth cement, and then recovering the tin from' the solution.

10. ln the electrolytic treatment of anode slimes to separate the metals contained therein, the process which comprises the smelting y to a metallic state and casting the same into anode plates, passing a current from said plate as an anode to a cathode separated from the anode by a semi-permeable diaphragm through an electrolyte capable oit combining with lead to form an insoluble salt and tohold the tin and bismuth senic, interposinga energias' in solution, recipitating the bismuth as a cement bfy a ding an excess of metallic tin tothe solution and then recovering the tin.

11. ln the electrolytic treatment of anode slimes containing tin, bismuth, lead, arsenic and the precious metals, to recover the metals, contained therein, the process which comprises the smelting of the slimes to a metallic state and casting plates, passing a current ot appropriate voltage and amperage from said plates as anodes to cathodes separated from the anode by a porous diaphragm through an anolyte containing approximately 18 0 ot hydrochloric acid to take the tin and bismuth in solution and deposit metallic Hold, silver, arsenic and insoluble salts ot cad as slirnes, separating the slimes from the solution, add-a ing a metal having a higher potential than bismuth to precipitate the met-als having a lower potential contained in the solution, and then treating said solution to recover the tin.

Signed at Perth Amboy, in the county of Middlesex andl State et New Jersey, this th day et December, A. 10.1921.

JAMES RBERT STAGK,

the same into anode 

